A central premise of bioclimatic envelope modeling is the assumption of niche conservatism. Whereas such assumptions are testable in modern populations, it is unclear whether niche conservatism holds over deeper time spans and over very large geographic ranges. Hyaenids occupied a diversity of ecological niches over time and space, and until the end-Pleistocene they occurred in Europe and most of Asia, with Asian populations of Crocuta suggested as being genetically distinct from their closest living relatives. Further, little is known regarding whether and how the dietary ecology of extinct populations of Crocuta differed from those of their extant African counterparts. Here, we use a multiproxy approach to assess an assumption of conserved dietary ecology in late Pleistocene extant spotted hyenas via finite element analysis, dental microwear texture analysis, and a novel dental macrowear method (i.e., whether teeth are minimally, moderately, or extremely worn, as defined by degree of dentin exposure) proposed here. Results from finite element simulations of the masticatory apparatus of Chinese and African Crocuta demonstrate lower skull stiffness and higher stress in the orbital region of the former when biting with carnassial teeth, suggesting that Chinese Crocuta could not process prey with the same degree of efficiency as extant Crocuta crocuta. Dental microwear texture data further support this interpretation, as Chinese Crocuta have intermediate and indistinguishable complexity values (indicative of hard-object feeding) between the extant African lion (Panthera leo) and extant hyenas (C. crocuta, Hyaena hyaena, and Parahyaena brunnea), being most similar to the omnivorous P. brunnea. The use of dental macrowear to infer dietary behavior may also be possible in extinct taxa, as evinced by dietary correlations between extant African feliforms and dental macrowear assignments. Collectively, this multiproxy analysis suggests that Chinese Crocuta may have exhibited dietary behavior distinct from that of living C. crocuta, and assumptions of niche conservatism may mask significant dietary variation in species broadly distributed in time and space.

No description available.

Topographically complex regions on land and in the oceans feature hotspots of biodiversity that reflect geological influences on ecological and evolutionary processes. Over geologic time, topographic diversity gradients wax and wane over millions of years, tracking tectonic or climatic history. Topographic diversity gradients from the present day and the past can result from the generation of species by vicariance or from the accumulation of species from dispersal into a region with strong environmental gradients. Biological and geological approaches must be integrated to test alternative models of diversification along topographic gradients. Reciprocal illumination among phylogenetic, phylogeographic, ecological, paleontological, tectonic, and climatic perspectives is an emerging frontier of biogeographic research.

The saber-toothed cat, Smilodon fatalis, and American lion, Panthera atrox, were among the largest terrestrial carnivores that lived during the Pleistocene, going extinct along with other megafauna ~12,000 years ago. Previous work suggests that times were difficult at La Brea (California) during the late Pleistocene, as nearly all carnivores have greater incidences of tooth breakage (used to infer greater carcass utilization) compared to today. As Dental Microwear Texture Analysis (DMTA) can differentiate between levels of bone consumption in extant carnivores, we use DMTA to clarify the dietary niches of extinct carnivorans from La Brea. Specifically, we test the hypothesis that times were tough at La Brea with carnivorous taxa utilizing more of the carcasses. Our results show no evidence of bone crushing by P. atrox, with DMTA attributes most similar to the extant cheetah, Acinonyx jubatus, which actively avoids bone. In contrast, S. fatalis has DMTA attributes most similar to the African lion Panthera leo, implying that S. fatalis did not avoid bone to the extent previously suggested by SEM microwear data. DMTA characters most indicative of bone consumption (i.e., complexity and textural fill volume) suggest that carcass utilization by the extinct carnivorans was not necessarily more complete during the Pleistocene at La Brea; thus, times may not have been "tougher" than the present. Additionally, minor to no significant differences in DMTA attributes from older (~30-35 Ka) to younger (~11.5 Ka) deposits offer little evidence that declining prey resources were a primary cause of extinction for these large cats.

Until now, the pre-Miocene fossil record of mustelids in North America has been restricted to specimens attributable to oligobunine taxa and isolated remains tentatively allocated to the genus Plesictis. In the present study, we report on a nearly complete cranium and a referred dentary of a new genus and species of mustelid. The specimens were recovered from the Turtle Cove and Kimberly Members of the John Day Formation, Oregon, USA. These excellently preserved specimens more confidently confirm the presence of mustelids in the Early and Late Oligocene (Early and Late Arikareean) of North America. Like the holotype specimen of 'Plesictis' julieni, the new species lacks an alisphenoid canal and a postprotocrista on the M1 (synapomorphies of Mustelidae), but retains a dorsally deep suprameatal fossa (a feature occasionally suggested to be unique to Procyonidae). Phylogenetic analyses, applying parsimony and Bayesian inference to combined molecular (five genes totalling 5490 bp) and morphological data, recover this new species of mustelid as sister-species to 'Plesictis' julieni. The results of these analyses reveal that the new genus is a close relative of other species of Plesictis and several taxa traditionally allied with Oligobuninae, thereby rendering Oligobuninae paraphyletic. We further discuss the significance of the relatively small size of this new mustelid as it relates to predictions based on increased aridification of the palaeoclimate and the expansion of open habitats in the Oligocene.

Text-related oral participation is ubiquitous in literacy and language instruction. As such, considering how invitations to these interactions are framed is critical, as this framing is directly implicated in the design of equitable classrooms. In this Teaching Tip, one common technique teachers have been encouraged to use—a class set of “equity sticks”—is reconsidered through the lens of asset-based instruction for all learners including emergent bilinguals (EBs). Reframing how EBs are invited to respond to texts requires that teachers get to know their students, privilege multilingualism, provide scaffolding for oral discussion, and encourage responses that transcend linguistic modalities.

Radar for biomass estimation has been widely investigated for temperate, boreal and tropical forests, yet tropical savanna woodlands, which generally form non-continuous cover canopies or sparse woodlands, have been largely neglected in biomass studies. This thesis evaluates the capability of Synthetic Aperture Radar (SAR) for estimating the above-ground biomass of the woody vegetation in a savanna in Belize, Central America. This is achieved by evaluating (i) polarimetric Synthetic Aperture Radar (SAR) backscatter and (ii) single-pass shortwave interferometric SAR (InSAR) as indicators of above-ground biomass. Specifically, the effect on SAR backscatter of woody vegetation structure such as canopy cover, basal area, vegetation height and above-ground biomass is evaluated. Since vegetation height is often correlated to above-ground biomass, the effectiveness of vegetation height retrieval from InSAR is evaluated as an indicator of above-ground biomass. The study area, situated in Belize, is representative of Central American savannas. Radar data used are AIRSAR fully polarimetric L- and P-band SAR, and AIRSAR C-band InSAR, Intermap Technologies STAR-3i X-band InSAR, and Shuttle Radar Topography Mission (SRTM) C-band InSAR. The field data comprise accurately georeferenced three-dimensional measurements for 1,133 trees and shrubs and 75 palmetto clumps and thickets in a transect of 800 m x 60 m which spans the main savanna vegetation strata of the study area. An additional 2,464 ground points were observed. Results show that savanna woodlands present a challenge for radar remote sensing methods due to the sparse and heterogeneous nature of savanna woodlands. Long-wave SAR backscatter is dominated not only by high biomass areas, but also by areas of leafy palmetto which have low vegetative biomass. Retrieved woodland canopy heights from X- and C-band InSAR are indicative of the general patterns of tree height, although retrieved heights are underestimated. The amount of underestimation is variable across the different canopy conditions. Of these two methods, the shortwave InSAR data give a better indication of the spatial distribution of the above-ground biomass of the woody vegetation in the savannas than SAR backscatter. These results have implications for new and planned future global biomass estimation missions, such as ALOS PALSAR, ESA’s planned P-band BIOMASS and TanDEM-X. Without appropriate mediation, SAR backscatter methods might overestimate above-ground biomass of the woody vegetation of savannas while InSAR height retrieval methods might underestimate biomass estimates. Some possible mediating approaches are discussed.

This thesis is formatted in journal style, and as is typical of research submitted to peer-reviewed journals, some of the data included in the three research chapters have been collected by collaborating authors. These authors are listed at the beginning of each chapter, and the contribution of each is detailed below. Chapter 2 incorporates a vegetation survey around the shores of the field site, Laguna La Gaiba, conducted by Ezequiel Chavez and René Guillén of the Muséo de Historía Natural Noel Kempff Mercado, Santa Cruz, Bolivia, and Michael J. Burn differentiated the pollen of Moraceae and Urticaceae in twenty-five horizons. Toby Pennington of the Royal Botanic Gardens, Edinburgh, has been crucial to data interpretation and discussion. The research in Chapter 3 also relies on the field surveys of Ezequiel Chavez and René Guillén, as well as the finer-scale pollen differentiation provided by Michael J. Burn. This chapter also includes carbon isotope data obtained by Neil J. Loader and Alayne Street-Perrott, Swansea University, Wales, and elemental data collected by Francis E. Mayle and Michael H. Marshall (Aberystwyth) at the Itrax XRF scanner facility, University of Aberystwyth. As in the preceding chapter, Toby Pennington has played an integral role in the ecological interpretation and climatic significance of changes in the inundation-tolerant forest. The data obtained for Chapter 4 were collected entirely by my own hand, but the interpretation of these data was improved by contributed work of my co-authors in the previous two chapters.

Sediment flux from the Alps shows a sharp increase around the Mio-Pliocene boundary (~5 Ma). This observation, linked to the exhumation of the Swiss Molasse basin since ca. 5-4 Ma has led to the suggestion that the Alps experienced accelerated exhumation and isostatic uplift at the orogen scale since this time. The core objectives of this thesis are to assess whether we can document post 5 Ma exhumation of the Alps and its spatial and temporal development, and to review the different potential (tectonic or climatic) factors controlling this denudation. I have developed a novel technique that uses isoage contours associated with age-elevation relationships to exploit the unique density of fission-track ages in the western European Alps, reconstruct cooling isoage surfaces and estimate exhumation rates on the orogen scale between 13.5 and 2.5 Ma. The exhumation histories reconstructed for eight areas of the Western Alps display strong similarities in timing and rate with orogen-wide average denudation rates inferred from sediment volumes. Exhumation rates increased more than twofold since Late Miocene times, and may have been locally modulated by the distinct response of different tectonic units. I then searched for correlation between the spatial pattern of long-term exhumation rates, from the apatite fission-track record, and potential controlling parameters. In the Western Alps, long-term exhumation rates correlate strongly with presentday rates of rock uplift, implying that the rock uplift pattern observed today is ancient. I also observed that the spatial pattern of released seismic energy does not correlate with rock uplift or exhumation, which suggests that exhumation is controlled by isostatic rebound rather than by active tectonic uplift. The lack of correlation between exhumation rates and the presentday distribution of precipitation suggests that the present-day pattern is either non representative of the long-term trend or that factors other than precipitation rate dominate the intensity of exhumation. In order to study the exhumation history in more detail, I sampled two elevation profiles in the central Aar massif (Switzerland) and the western Lepontine Alps (Italy) for AFT and AHe dating which are characterised by steep age-elevation relationships around 8 and 4 Ma. I used the Pecube model to predict AFT and AHe ages according to several tens of exhumation scenarios and compared modeled and measured ages. The results of numerical modeling do not reject the hypothesis of two exhumation pulses at 9-7 and 5-3 Ma in the Aar massif. However, this signal is not detected in the Lepontine Alps, and contingent upon further flexural modeling, the exhumation recorded in the Aar massif since 5 Ma does not match the amount required to explain the denudation in the Swiss Molasse basin by flexural isostatic rebound. Rather, the data hint at an additional mechanism of rock uplift, such as the delamination of lithospheric mantle.

Granitic magmatism in collision belts is widely regarded as a major mechanism for generating continental crust. This hypothesis can be tested by identifying the source rocks of granitic magmas, and in particular the contribution by pristine mantle material. The complexity of granites, and their susceptibility to post-crystallisation alteration, has until recently provided a major obstacle to progress. Zircon, a common and chemically robust accessory mineral in granitoid rocks, retains a record of the composition of the magma it grew from. Recent developments in microanalysis (ion microprobe and laser ablation ICP-MS) now enable in-situ analysis of zircon crystals at high spatial resolution and precision, providing access to this record at the previously inaccessible intra-crystal scale. The resulting data have enormous potential to provide new insights into the nature and age of source rocks and the processes driving magma evolution. This project used an integrated in-situ O, U-Pb and Hf isotope, trace and rare earth element study of zircon to identify the sources and chart the evolution of two ‘I-type’ (igneous/infracrustal precursor) Scottish late Caledonian (~430-400 Ma) granite plutons. I have constrained models of magma generation, the relative contributions of mantle and crust, the ages and identities of their lower crustal sources, and have shown that the plutons played, at most, a minor role in crustal growth. In addition, I have been able to resolve the extent to which open-system changes like magma mixing affected the magma compositions. The same approach was used in a pilot study of three Caledonian (~460 Ma) ‘S-type’ (sedimentary/supracrustal precursor) granite plutons, which theoretically represent magmas formed by melting of a purely supracrustal source. The data confirm that Dalradian country rocks were the primary source, but reveal remarkable isotopic diversity within and amongst the three plutons. The most important general conclusion from this PhD study is that the complexity and scale of isotopic heterogeneity between plutons, amongst samples of the same pluton, in single samples and within individual crystals is far greater than previously recognised, consistent with the incremental assembly of plutons from multiple melt batches of differing composition, sources and petrogenetic evolution.